1. Field of the Invention
The present invention relates to an electron beam apparatus, an image display apparatus, a television apparatus, and a spacer used for an airtight vessel including these apparatuses, which are particularly preferably used for an electron beam apparatus having a plurality of electron emitting devices and a spacer covered with resistance films.
2. Related Background Art
In the case of an image forming apparatus constituted by a first substrate at the electron source side and a second substrate at the display face side which are faced with each other by keeping an interval, a spacer constituted by an insulating material is generally held between the first and second substrates in order to obtain a necessary atmospheric resistance. However, a problem occurs that the spacer is electrified to influence an electron trajectory nearby the spacer and to cause a luminescence position shift. This becomes a cause of image deterioration such as luminescence brightness deterioration or color ooze of a pixel nearby the spacer.
It is conventionally known to use a spacer covered with a resistance film in order to prevent the spacer from being electrified.
Specifically, the following spacers are known: a rib-like spacer covered with a resistance film, in which the resistance film is held between the wiring of a first substrate and the electrode of a second substrate so that the resistance film is directly pressure-welded to the wiring and the electrode; and a spacer covered with a resistance film, in which spacer electrodes are on the upside and the downside of the spacer so that the resistance film is in contact with the wiring and the electrode through the spacer electrodes (refer to Patent Document 1).
[Patent Document 1] Japanese Patent Application Laid-Open No. H08-180821
However, as a result of studying the image forming apparatus described in Patent Document 1 by the present inventor et al., we newly find that in the case of a spacer in which an end face of the spacer is covered with a resistance film, when directly pressure-welding the resistance film to the wiring of a first substrate and the electrode of a second substrate, electrification of the spacer may not be sufficiently canceled or the potential distribution of the surface of the spacer may show an unexpected distribution state.
It is difficult to specify the cause by which the above phenomena occur because the cause often depends on the fabrication process of a display apparatus. However, when a strain occurs on the wiring of the first substrate or the electrode of the second substrate or a foreign matter is present on it, a contact position between the resistance film of the spacer and the wiring or electrode is fluctuated depending on a place because the surface of the wiring or electrode is roughened or burrs, etc. It is found that the potential distribution is thus disordered. In particular, in the case of a wiring manufactured by an inexpensive manufacturing method, the surface shape may be locally different and the above imperfect electrical connection easily occurs.
In the above case, electrification of the spacer is not sufficiently solved and moreover, an irregular change occurs in the potential distribution of the surface of the spacer, and a trouble occurs that the trajectory of an electron beam does not conform to the design. Moreover, because the electron beam is accelerated from the first substrate toward the second substrate, a change of the trajectory remarkably appears due to a deflection force at the first substrate side compared to the second substrate side.
The deflection of the electron beam due to the potential distribution of the surface of the spacer at the first substrate side is more specifically described below by referring to FIGS. 11 and 12.
FIG. 11 is a local sectional view of a rib-like spacer 3 covered with a resistance film 14 when inserting it along a wiring 5 of the first substrate when viewed from the orthogonal direction. FIG. 12 shows an enlarged contact portion between the resistance film 14 and the wiring 5 shown in FIG. 11, which is a schematic view showing the potential distribution and electron trajectory when the contact position between the spacer and the wiring is shifted from the center because the surface of the wiring 5 is roughened.
As shown in FIG. 12, relations of the contact position between the resistance film 14 and the wiring 5 are asymmetric to the center of the spacer 3. When assuming distances between the center and contact ends of the spacer 3 as L1 and L2, the potential at the L1 side is raised by a voltage drop due to the resistance between L2 and L1 (equal potential line 20). Thus, the trajectory of an electron beam emitted from an electron emitting device 8 at the L1 side shows a behavior different from the trajectory of electrons emitted from the electron emitting device at the L2 side. As a result, images differ (are deflected) at L1 side and L2 side because the attainment position of the electron beam is shifted (electron beam trajectory 18).
However, in the case of the image forming apparatus described in Patent Document 1, in which the spacer electrodes are set at the upside and downside of the spacer covered with the resistance film and the resistance film is connected to the wiring of the first substrate and the electrode of the second substrate through the spacer electrodes, because the spacer electrodes are exposed to the sides of the spacer, electric field distribution occurs nearby the exposed portions. Though the electric field distribution is almost uniform in the longitudinal direction of the spacer, it appears strongly compared to the case in which the spacer electrodes are not exposed. Therefore, it is found that the attainment position of an electron beam emitted from an adjacent electron emitting device is easily greatly disordered due to a shift of alignment caused when setting the spacer, and moreover, this becomes a cause of emission, and the quality of an image is likely to be greatly deteriorated. To prevent this, it is necessary to set the spacer electrodes so as not to be exposed to the sides of the spacer or accurately set the spacer. Anyway, this causes cost increase.